Source: USA Today:

The newspaper USA Today researched and compiled all the fees charged by U.S. airlines, from check-in through landing, in a series of fairly comprehensive charts. Leg room, frequent flier usage, bag sizes, and more are covered in their wallet-deflating infamy.

For instance when you book a round-trip ticket by phone, American, Continental and Delta will charge $20. Whereas United and US Airways charge $25.

You will be poorer by $35 for every 1000 miles that you buy from Continental One-Pass program. While United Frequent Flyer program will cost you $67.25/1000 miles.